640999554 has 32 divisors (see below), whose sum is σ = 1388272704. Its totient is φ = 196136640.

The previous prime is 640999549. The next prime is 640999577. The reversal of 640999554 is 455999046.

It is a junction number, because it is equal to n+sod(n) for n = 640999497 and 640999506.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8584 + ... + 36819.

It is an arithmetic number, because the mean of its divisors is an integer number (43383522).

Almost surely, 2^640999554 is an apocalyptic number.

640999554 is an abundant number, since it is smaller than the sum of its proper divisors (747273150).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640999554 is a wasteful number, since it uses less digits than its factorization.

640999554 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45602.

The product of its (nonzero) digits is 1749600, while the sum is 51.

The square root of 640999554 is about 25317.9689943724. The cubic root of 640999554 is about 862.2222830301. Note that the first 4 decimals are identical.

The spelling of 640999554 in words is "six hundred forty million, nine hundred ninety-nine thousand, five hundred fifty-four".